JPH0343698Y2 - - Google Patents

Description

[Detailed explanation of the idea] Industrial applications This invention relates to a transformer for microwave ovens.

Prior Art FIG. 3 shows a wiring diagram of a conventional microwave oven, which includes a microwave oven transformer 1, a magnetron 50, a capacitor 41, and a diode 42.
It is composed of. In the figure, the core 2 of the microwave oven transformer 1 includes a primary coil 10 for power supply, a secondary high voltage coil 20 for supplying high voltage power to the magnetron 50, and a heater for powering the cathode 51 of the magnetron 50. A coil 40 is wound. A winding start portion 21A of the secondary high voltage coil 20 is connected to the ground 9 via the core 2. At the winding end portion 25A of the secondary high voltage coil 20,
A capacitor 41 and a diode 42 are connected in series, and the output side of the diode 42 is connected to the ground 9. The input side of the diode 42 is the cathode 5
Connected to 1. Anode 5 of magnetron 50
2 is connected to ground 9.

FIG. 4 shows a perspective view of a conventional microwave oven transformer. The core 2 of the microwave oven transformer 1 is
It is composed of an E-shaped core 3 and an I-shaped core 4 in contact with the E-shaped core 3, and the outer surfaces of both 3 and 4 are joined and fixed by welding. The middle leg 3A of the E-type core 3 has a secondary high voltage coil 20 in which enamel coated wire is wound and laminated.
The primary coil 10 and heater coil 40 (not shown) are fitted and inserted. As described above, the low voltage terminal 26A is connected to the winding start portion 21A, and the low voltage terminal 26A is fixed to the core 2.
Core 2 is connected to ground 9 by means not shown. The winding end portion 25A is connected to the high voltage terminal 22A so that it can be connected to the capacitor 41 described above.

Problems to be Solved by the Invention In the conventional microwave oven transformer 1, the winding start part 21A is connected to the ground (not shown) via the low voltage terminal 26A and the core 2. 2 up to the end 25A
High voltage is also generated in the outer peripheral coil 24 of the next high voltage coil 20. On the other hand, since this outer circumferential coil 24 is close to the inner wall 3B of the core 2 which is connected to the ground 9, it is necessary to insulate the outer circumferential coil 24 and the inner wall 3B with an inner wall insulator 5 such as insulating paper. There is. Therefore, the number of steps for inserting the inner wall insulator 5 is increased, and the productivity of the microwave oven transformer 1 is reduced. Note that the inner circumferential coil of the secondary high voltage coil 20 generates only a low voltage because it is close to the winding start portion 21A, but this inner circumferential coil contacts the middle leg portion 3A and the secondary high voltage coil 20 generates a low voltage. In order to prevent the enamel coating from being damaged, a midfoot insulator 6 is inserted between the midfoot portion 3A of the E-shaped core 3 and the secondary high voltage coil 20.

Measures to solve the problem Wrap the secondary high voltage coil around an insulating bobbin,
Next, connect the beginning of the high voltage coil to the high voltage side, and connect the end of the winding to the ground.

Function The bobbin maintains insulation between the high voltage side of the secondary high voltage coil and the core.

DETAILED DESCRIPTION OF THE INVENTION FIG. 1 shows a perspective view of a secondary high voltage coil assembly 200 installed in a microwave oven transformer according to the present invention. A secondary high voltage coil 20 is wound around a hollow, substantially prismatic bobbin 30 that is integrally molded from synthetic resin. That is, a single enamelled wire with a small wire diameter is wound and laminated, and a high voltage terminal 22 is attached to the winding start portion 21 of this enameled wire, and a high voltage terminal 22 is attached to the winding end portion 25 of the enameled wire.
A low voltage terminal 26 is attached to each. A notch 31 having a depth approximately equal to the thickness of the secondary high-voltage coil 20 is formed in the upper surface 35 of the bobbin 30 to facilitate pulling out of the winding start portion 21 from the bobbin 30. Further, a small notch 32 is provided on the upper surface of the bobbin 30 at a position substantially opposite to the notch 31, so that the winding end portion 25 can be easily drawn out. Furthermore, bobbin 30 has bobbin 3.
A barrier 33 is formed integrally with 0. The barrier 33 has a rectangular shape formed perpendicularly to the upper surface 35 between the notch 31 and the hollow part 36 of the bobbin 30, and has the role of insulating the winding start part 21 from the core (not shown). There is.

FIG. 2a shows a perspective view of a transformer for a microwave oven according to the present invention. After inserting and fitting the middle leg portion 3A of the E-type core 3 into the hollow portion 36, the I-type core 4 is bridged over the upper end surface of the E-type core 3, and the contact outer peripheral surfaces of both 3 and 4 are Join and fix by welding. The winding end portion 25 is connected to ground via a low voltage terminal 26 by a circuit not shown. Therefore, although high voltage is applied to the winding start section 21 when the microwave oven transformer is in operation, it is insulated from the core 2 by the barrier 33.

FIG. 2b shows a schematic view of the section AA in FIG. 2a. As described above, since the winding end portion 25 is connected to the ground (not shown), high voltage is applied to the winding start portion 21 and the secondary high voltage coil 20 wound subsequently. This high voltage decreases as it approaches the winding end 25, and finally reaches zero voltage, ie, the same potential as ground, at the winding end 25. The secondary high voltage coil 20 described above is connected to the middle leg 3A of the E-type core 3 and the inner wall 4B of the I-type core 4 by means of the bobbin 30.
In other words, it is insulated from the core 2.

Note that the outer peripheral coil 24 of the secondary high voltage coil 20
is not insulated from the inner wall 3B of the E-type core 3 by the bobbin 30, but as described above, the end portion 25 of the winding is connected to the ground.
The outer peripheral coil 24, which is a coil near 5, has
Since only extremely low voltage is applied, bobbin 30
Therefore, there is no need to insulate it from the inner wall 3B.

As mentioned above, a microwave oven transformer has a primary coil, a secondary high-voltage coil, and a heater coil, but the description of the primary coil and heater coil is omitted in Figures 1 and 2. There is.

Further, as described above, the winding end portion 25 is connected to the ground via the low voltage terminal 26, but specifically, the low voltage terminal 26 is fixed to the core 2 and the core 2 is connected to the ground, or the core 2 is connected to the ground. Core 2 connected to
For example, the low voltage terminal 26 is connected to a terminal plate welded by spot welding or the like, or it is connected to a low voltage terminal plate formed in the same way as the high voltage terminal plate 23 formed on the upper surface 35 of the bobbin 30. The board may be connected to earth.

Effects of the invention As explained above, according to this invention, the secondary high voltage coil is wound around the bobbin, the end of the winding is connected to the ground, the beginning of the winding is connected to the high voltage side, and the hollow part of the bobbin is After inserting the middle leg of the mold core,
Since the I-type core is brought into contact with the upper end surface of the type core, the high-voltage portion of the secondary high-voltage coil is insulated from the core 2 by the bobbin.

Therefore, it is possible to eliminate the inner wall insulator and mid-leg insulation that were conventionally required between the secondary high-voltage coil and the inner wall of the core, so a significant improvement in productivity can be expected. Furthermore, damage to the enamel coating of the secondary high voltage coil due to contact between the secondary high voltage coil and the core can be prevented.

[Brief explanation of the drawing]

Figure 1 is a perspective view of a secondary high voltage coil assembly used in a microwave oven transformer according to the present invention;
Figure a is a perspective view of a microwave oven transformer according to the present invention, Figure 2b is a schematic longitudinal sectional front view of Figure 2a, and Figure 3
The figure shows a wiring diagram of a conventional microwave oven, and FIG. 4 shows a perspective view of a conventional transformer for a microwave oven. 1...Transformer for microwave oven, 2...Core, 3
...E-type core, 3A...midfoot, 3B, 4B...
Inner wall, 4... I-type core, 5... Inner wall insulator, 9...
...Earth, 20...Secondary high voltage coil, 21, 21
A... Winding start part, 22... High voltage terminal, 23... High voltage terminal plate, 24... Outer circumference coil, 25, 25A
... End of roll, 26, 26A ... Low voltage terminal board, 3
0... Bobbin, 31, 32... Notch, 33...
Barrier, 35...Top surface, 200...Secondary high voltage coil assembly.

Claims (1)

[Scope of utility model registration request] A transformer for a microwave oven characterized by having a secondary high voltage coil wound around a bobbin, the beginning of which is connected to the high voltage side, and the end of the coil being connected to ground.